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What ExperTune Needs to Know About Your PID Algorithm
ExperTune Analysis and Tuning software includes a database of over 500 industrial PID controllers. If you
have a controller that is not in our list we would like to add it for you. With detailed information about the
controller, we can accurately tune and simulate its response with your process. To add a new controller, we
need documentation describing it.

There simply is no way to analytically tune a controller if you do not know the type of algorithm and
the units.
GET MORE INFO
Request Quote The Difference Equation is the best
On-Line Presentation
Ideally the most complete information on the controller is the difference equations. These equations
Get Payback CD describe the digital operation of the controller as implemented in software. For example, here are the
difference equations for a simple PID controller:
CUSTOMERS TALK et = PVt - SPt
xt = xt-1 + et-1 T / I
yt = Gain[et + xt + (et - et-1) D / T]

(NOTE: This simple example has no reset windup, no derivative gain limit and has
derivative action on error.)

With this information we can very accurately simulate and tune your controller.

Laplace Domain Equation
If you can't get the difference equation then we need a Laplace domain equation that describes the
controller. Something like this, for example:

X = Gain[E s + E/(I s) + D s]

(NOTE: Again this a simplified example.)

Other information we need
Does the controller use: Proportional band or Gain?
What are the units on the controller integral action: min/rep, rep/min, sec/rep or rep/sec?
What are the units on the controller derivative action: min, sec?
Does the controller use multipliers on the gain, integral and derivative? For example on some
controllers, when you dial in 2000 for the gain, the actual gain is 2. This example has an implied
decimal point.
What other controller options are there for this algorithm. Does it have a gain on PV or gain on
error option? Does it have a D on PV or D on error option?

If you do not have the difference equation we also need
Laplace domain equation (s domain) above.

Does the controller use anti-reset windup? If so, describe how it works.
Does the controller use a D gain limit or derivative filter? If so, what is the time constant of the
filter in proportion to the D action?

If you do not have the difference equation or the Laplace equation
We will need to know the name of the type of algorithm used. Is it ideal, parallel or series? Relying on this
answer is risky, since there are no standards. See Comparison of PID Control Algorithms

Other useful stuff we'd like
What are the allowable ranges for P, I, and D?